# coding: utf-8

import functools


def memoize(fn):
    known = dict()

    @functools.wraps(fn)
    def memoizer(*args):
        if args not in known:
            known[args] = fn(*args)
        return known[args]

    return memoizer


@memoize
def nsum(n):
    # 回傳前 n 個數字和
    assert(n >= 0), 'n must be >= 0'
    return 0 if n == 0 else n + nsum(n-1)


@memoize
def fibonacci(n):
    # 費波那契數列的第 n 個數
    assert(n >= 0), 'n must be >= 0'
    return n if n in (0, 1) else fibonacci(n-1) + fibonacci(n-2)


if __name__ == '__main__':
    from timeit import Timer
    measure = [{'exec': 'fibonacci(100)', 'import': 'fibonacci', 'func': fibonacci},
               {'exec': 'nsum(200)', 'import': 'nsum', 'func': nsum}]

    for m in measure:
        t = Timer('{}'.format(m['exec']),
                  'from __main__ import {}'.format(m['import']))

        print('name: {}, doc: {}, executing: {}, time: {}'.format(m['func'].__name__,
                                                                  m['func'].__doc__,
                                                                  m['exec'], t.timeit()))
